Web Services. Moving towards Service Oriented Architectures. Rensselaer CSCI 4220 Network Programming

Transcription

1 Web Services Moving towards Service Oriented Architectures Rensselaer CSCI 4220 Network Programming

2 Agenda Service Oriented Architectures (SOA) Web Services Simple Object Access Protocol (SOAP) Web Services Description Language (WSDL) Universal Description, Discovery, and Integration (UDDI) Tools Examples Grid Services

3 Service Oriented Architecture (SOA) SOAD vs. OOAD New Services Flows Components Services Layer Placed on top of existing products Roles Service provider Service consumer

4 Service Oriented Architecture (SOA) Architectural style that defines an interaction model between 3 primary parties Service Provider Publishes a service description and provides the implementation for the service Service Consumer Uses either the uniform resource identifier (URI) for the service description directly or can find the service description in a service registry Service Broker Provides and maintains the service registry, although nowadays public registries are not in vogue.

5 Service Oriented Architecture (SOA) When To Use SOA Heterogeneous Environment Present Real-time Performance is not critical Dynamic Information Loose Coupling

6 Service Oriented Architecture (SOA) SOA Design Strategy Top Down Strategic and Business Aligned Stems from Business Process Choreography Web Services Bottom Up Tactical Implementation of SOA Stems from existing components

7 Services Layer Service Types Stateless Service Message exchanges, no information transferred from persistent resources Conversational Service Implements a series of operations Stateful Service Provides access to, or manipulates a set of logical stateful resources (documents or data sets)

8 Service Layer Implementation Web Services System Identified by a URI XML defined interfaces and bindings Discoverable by other software system Other systems interact with the Web service based on its definition XML based messages between systems

9 Web Services 1. WS 2. RE 3. WS- Interface 4. Message Processing 5. Requests 6. Message Dispatch 7. Stateful Resource

10 Web Services Protocol Stack Similar to TCP/IP DISCOVER (UDDI) DESCRIBE (WSDL) ACCESS (SOAP) STRUCTURE (XML) TRANSPORT (HTTP)

11 Simple Object Access Protocol (SOAP) XML message protocol to access web services HTTP Header SOAP Envelope SOAP Header Header SOAP Body Application Specific Message Data

12 SOAP Travel WS Example <?xml version='1.0'?> <env:envelope xmlns:env=" <env:header> <m:reservation xmlns:m=" env:role=" env:mustunderstand="true"> <m:reference>uuid:093a2da1-q r-ba5dpqff98fe8j7d</m:reference> <m:dateandtime> t13:20: :00</m:dateandtime> </m:reservation> <n:passenger xmlns:n=" env:role=" env:mustunderstand="true"> <n:name>åke Jógvan Øyvind</n:name> </n:passenger> </env:header> <env:body> <p:itinerary xmlns:p=" vel"> <p:departure> <p:departing>new York</p:departing> <p:arriving>los Angeles</p:arriving> <p:departuredate> </p:departuredate> <p:departuretime>late afternoon</p:departuretime> <p:seatpreference>aisle</p:seatpreference> </p:departure> <p:return> <p:departing>los Angeles</p:departing> <p:arriving>new York</p:arriving> <p:departuredate> </p:departuredate> <p:departuretime>mid-morning</p:departuretime> <p:seatpreference/> </p:return> </p:itinerary> <q:lodging xmlns:q=" tels"> <q:preference>none</q:preference> </q:lodging> </env:body> </env:envelope>

13 Describing Web Services WSDL Web Service Definition Language Defines Web service can do Where it resides How to invoke it WSDL PortType Message Binding DataTypes

14 WSDL Types Service Interface Contains Types, import, message, porttype, and binding elements. A service interface contains the WSDL service definition that will be used to implement one or more services. It is an abstract definition of a web service, and is used to describe a specific type of service Service Implementation Contains import and service elements.

15 WSDL Skeleton <definitions> <types> definition of data types... </types> <message> definition of a message... </message> <porttype> definition of a port {1 way req/resp illicit resp notification}... </porttype> <binding> definition of binding to SOAP... </binding> </definitions> [5]

16 WSDL Example <message name="gettermrequest"> <part name="term" type="xs:string"/> </message> <message name="gettermresponse"> <part name="value" type="xs:string"/> </message> <porttype name="glossaryterms"> <operation name="getterm"> <input message="gettermrequest"/> <output message="gettermresponse"/> </operation> </porttype> <binding type="glossaryterms" name="b1"> <soap:binding style="document" transport=" /> <operation> <soap:operation soapaction=" <input> <soap:body use="literal"/> </input> <output> <soap:body use="literal"/> </output> </operation> </binding>

17 UDDI Universal Description, Discovery, and Integration Registry of web services Phone book for web services[6] White pages Basic contact information and identifiers. Yellow pages Information that describes a web service Green pages Information that describes behaviors and functions of a web service WS-Inspection WS-Inspection is a new XML grammar that allows a Web server to be inspected for services that may be deployed.

18 UDDI Activities Using UDDI [7] Establishing Connection Publishing a Business Entity Classifying a Business Entity Publishing a Model Publishing a Service Deleting from a Registry

19 UDDI Data Types and Mapping UDDI DataTypes WSDL to UDDI Mapping

20 WSDL to UDDI Mapping

21 UDDI Process Flow

22 Tools Used in Examples Apache Software Foundation Xerces XML Schema processor SOAP Implementation (Axis Project is related) Library to enable invocation of SOAP services Tomcat Servlet Container which is the official Reference Implementation for the Java Servlet and JavaServer Pages technologies

23 Servlets and Containers Servlet A Java program that runs within a JVM on a web server and sends HTML data to a web browser Implements javax.servlet.servlet Servlet Container Web Server Component that interacts with Servlets Responsible for forwarding the requests and responses to the appropriate Servlet Maps URL s to Servlets

24 Servlet Containers How Java Web Servers Work HTTPServer Class How Servlet Containers Work Servlet is called for the first time Load the servlet class Call its init method (once only). For each request Construct an instance of javax.servlet.servletrequest Construct an instance of javax.servlet.servletresponse. Invoke the servlet's service method Pass the ServletRequest and ServletResponse objects to the servlet When the servlet class is shut down Call the servlet's destroy method and unload the servlet class. How Tomcat Works Entire book on the internal workings of Tomcat

25 Web Service Examples Automobile Finder Web Service WSDL Generation and Stub Generation Semantic Web Service Finder UDDI Publishing

26 Grid Services All Grid Services are Web Services Vice versus not true A web service that conforms to a set of conventions (interfaces and behaviors) that define how a client interacts with it

27 Grid Services OGSI Describe Grid Services Open Grid Services Infrastructure Extension upon WSDL Base for Open Grid Services Architecture (OGSA) Grid Services DISCOVER (UDDI) DESCRIBE (OGSI) ACCESS (SOAP) STRUCTURE (XML) Web Services DISCOVER (UDDI) DESCRIBE (WSDL) ACCESS (SOAP) STRUCTURE (XML) TRANSPORT (HTTP) TRANSPORT (HTTP)

28 OGSI Defines Grid Services (since 2002) WSDL 1.1 extensions (to be in WSDL 2.0) Discovery (Grid Handles and References) Dynamic Service Creation Lifetime Management Notification Manageability Fault Conventions

29 Existing Grid Services (1/2) GILDA SERVICE Resource Broker (RB) Resource Broker for DAG (RB) Information Index (BDII) Backup BDII LDAP (for GILDA VOs) GridICE Replica Location Service (RLS) HOST grid004.ct.infn.it grid007.ct.infn.it grid017.ct.infn.it grid018.ct.infn.it gridvo.cnaf.infn.it:10389 alifarm7.ct.infn.it:50080 grid008.ct.infn.it

30 Existing Grid Services (2/2) GILDA raster image

31 Reference [1] Semantic Web Book [2] IBM PPT [3] - monty [4] GILDA [5] - [6]- ex1.html [7] - um=2